F# impl

F#/Program.fs

@@ -0,0 +1,15 @@
+open System
+
+let encrypt (word : string) = 
+    let key = "KCQ"
+    [ 0..(word.Length - 1) ]
+    |> Seq.map (fun idx -> Convert.ToChar(Convert.ToInt32 word.[idx] ^^^ Convert.ToInt32 key.[idx % key.Length]))
+    |> String.Concat
+
+[<EntryPoint>]
+let main argv = 
+    let encrypted = encrypt "IzzyDev"
+    printfn "Encrypted: %s" encrypted
+    let decrypted = encrypt encrypted
+    printfn "Decrypted: %s" decrypted
+    0